The present invention relates to a lumbar support regulating apparatus and more particularly to a lumbar support regulating apparatus for vehicle and aircraft seats which regulates the firmness of a portion of the seat supporting the lumbar region of a seated person to improve the posture of the person.
Prior art apparatus of this type are disclosed in Japanese Patent Publication No. 56(1981)-10051, Japanese Patent Publication No. 61(1986)-73615 and Japanese Patent Publication No. 61(1986)-226006. In these prior art apparatus, a lumbar support member having a plate shape is rotatably supported by a rotatable shaft which extends laterally across the seat back thereby regulating the position of the lumbar support member and the pressing force on the lumbar region.
In Japanese Patent Publication No. 56-(1981)-10051, the wave shaped spring having a substantially S-shaped configuration is provided on a lumbar support portion and is forwardly and rearwardly removable. When the spring is moved forwardly and rearwardly, the configuration of the lumbar support portion is changed and the pressing force of the spring on the lumbar region of a human body is changed so that the hardness or firmness of the lumbar support portion is sensed the person is also changed. Since the durability of this type of spring is somewhat limited, it is necessary to restrict the degree of bending to a relatively small amount. As a result, the wave shaped spring having a large spring coefficient must be used. However, the amount of bending is restricted so the forward and rearward movable stroke of the lumbar support portion is quite small and the regulating range is very narrow. It is also possible with such a spring that a person seated on such a seat with the spring in its forward position will experience an unpleasant pain-like sensation due to the large spring coefficient.
In Japanese Patent Publication No. 61-(1986)-73615, the pressing member having a plate shaped is located in the lumbar support portion of the seat and a coil spring is disposed between the pressing member and a regulating member for regulating the position of the pressing member and the distance from the rotational center of the pressing member to the operating line of force of the coil spring is changed, thereby changing the spring coefficient of the lumbar support portion. However, the amount of movement of the pressing member is fairly large in the non-loaded state so that the posture of a seated person cannot be significant changed.
In Japanese Patent Publication No. 61-(1986)-226006, a pressing member having a plate shape is located in the lumbar support portion of the seat and the coil spring is interposed between the pressing member and a regulating member for regulating the position of the pressing member and the distance from the rotational center of the pressing member to the operating line of force of the coil spring is changed, thereby moving the pressing member forwardly and rearedly. However, when the receiving force on the pressing member from a seated person is large upon forward movement of the pressing member, it is necessary to use a coil spring having a large number of windings and a large diameter in order to obtain a fairly large change in posture regulation, and it is difficult to install such a coil spring within a seat back.